H3

import java.io.*;
import java.util.*;

public class oaks_md implements Runnable {
	private Scanner in;
	private PrintWriter out;

	public void run() {
		try {
			in = new Scanner(new FileReader("oaks.in"));
			out = new PrintWriter(new File("oaks.out"));
			solve();
			in.close();
			out.close();
		} catch (IOException e) {
			e.printStackTrace();
			System.exit(1);
		}
	}

	int n;
	int[] a;
	boolean[][] wipe;
	int[][] howWipe;
	int[] max;
	int[] how;

	public void solve() {
		n = in.nextInt();
		a = new int[n];
		wipe = new boolean[n][n];
		howWipe = new int[n][n];
		max = new int[n];
		how = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = in.nextInt();
		}
		for (int i = 0; i < n - 1; i++) {
			wipe[i][i + 1] = true;
			howWipe[i][i + 1] = -1;
		}
		for (int d = 2; d < n; d++) {
			for (int i = 0, j; (j = i + d) < n; i++) {
				for (int k = i + 1; k < j; k++) {
					if (a[k] > Math.max(a[i], a[j]) || a[k] < Math.min(a[i], a[j])) {
						if (wipe[i][k] && wipe[k][j]) {
							wipe[i][j] = true;
							howWipe[i][j] = k;
							break;
						}
					}
				}
			}
		}
		max[0] = 1;
		for (int i = 1; i < n; i++) {
			max[i] = 0;
			for (int j = 0; j < i; j++) {
				if (max[j] > 0 && wipe[j][i] && a[j] <= a[i] && max[j] + 1 > max[i]) {
					max[i] = max[j] + 1;
					how[i] = j;
				}
			}
		}
		if (max[n - 1] == 0) {
			out.println(-1);
			return;
		}
		out.println(n - max[n - 1]);
		cut(n - 1);
	}

	private void cut(int v) {
		if (v == 0)
			return;
		cut(how[v]);
		wipe(how[v], v);
	}

	private void wipe(int u, int v) {
		int w = howWipe[u][v];
		if (w < 0)
			return;
		wipe(u, w);
		wipe(w, v);
		out.println(w + 1);
	}

	public static void main(String[] args) throws IOException {
		Locale.setDefault(Locale.US);
		new Thread(new oaks_md()).start();
	}
}